Most modern aircraft have retractable landing gear, wheel wells for receiving the landing gear while the aircraft is in flight, and hatches for closing the wheel wells. The hatches are opened and closed with the help of hatch operating actuators, e.g. hydraulic actuators.
When the hatch reaches the closed position, it is automatically locked in this position by hooking means, e.g. a hooking box having a hook hinged thereto that holds captive a roller fastened to the hatch. The hook is unhooked with the help of an actuator, usually a hydromechanical or an electromechanical actuator. Often the hooking box includes an emergency actuator capable of unlocking the hook in the event of it not being possible to use the main actuator.
In flight, the unhooking of the hook and the opening and closing of the hatch are controlled during sequences for extending and retracting the landing gear. It should be observed that the hatches are reclosed and hooked once the landing gear has been deployed.
When the aircraft is on the ground, it is necessary to be able to open the hatches, in particular in order to access equipment situated on the top portion of an undercarriage or in the wheel well. For this purpose, most aircraft include mechanical control means that are operable by personnel on the ground and making it possible to deactivate the hooking means in order to release the hatches.
These mechanical control means generally include a handle connected to the hooking box by a linkage, together with safety means for ensuring that the handle is not operated in untimely manner.
Those mechanical control means are particularly heavy, bulky, and therefore expensive for the aircraft manufacturer.